/* 
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.felix.framework.util.ldap;

/**
 * This class is used to create simple marker instances that are inserted
 * into the evaluation stack of a LDAP filter expression when an attribute
 * is referenced that has no defined value. These invalid marker instances
 * force the operators to throw an "unsupported type" exception, which the
 * evaluator catches and then converts the entire subexpression containing
 * the non-existent attribute to <tt>false</tt>.
**/
class Unknown
{
}
